Samuel whytb



UNITED STATES PATENT OFFICE.

SAMUEL WHYTE, OF REDHILL, ENGLAIVD.

PROCESS OF RESHARPENING FILES.

No Drawing.

To all whom it may concern Be it known that I, SAMUEL WI-IYTE,

B. So, a subject of the King of Great Britain and Ireland, and residingat Shir1ey, Earlswood- Road, Bedhill, in the county of Surrey, England,have invented certain new and useful Improvements Relating to Processesof Resharpening Files, of which the following is a specification.

This invention relates to the renewing of the cutting edges of files orother appliances having similar multiple cutting edges, by etching.

I have found that etching is produced upon file steels by hot dilutesulfuric acid, but that the action rapidly becomes not uniform. Theaction on the bottoms of the grooves between the teeth soon ceases, andthey become clogged, possibly with iron carbids set free. Again, dilutehydrochloric acid only acts very slowly, much too slowly for industrialworking. Dilute nitric acid, on the other hand, acts very rapidly, andtends to pit the surfaces. Its action alone is very difficult tocontrol. It has, however, the valuable property of very rapidly cleaningthe surfaces, and removing all clogging metal and other matter.

Now the present invention consists in employing. to renovate files andthe like, combinations of nitric and hydrochloric acids givingindustrially controllable etching.

In carrying this invention into effect, the ordinary worn files are,after cleaning, immersed in a warm bath of mixed nitric and hydrochloricacids, in substantially equal Specification of Letters Patent. PatentedAug, 26, 1919,

Application filed April 16, 1919.

Serial No. 290,575.

parts of these acids, and of water. The rate of etching depends on thetemperature of the bath, and this is maintained practically constant.-At about 80 F., the files will be found to take about eight minutes tocomplete, while if the bath be raised to about 100 F., they will becompleted in about four minutes. They are then removed from the bath,washed, and preferably wiped with oil, when they are ready 'for packing.

I employ suitable frames into which the files are inserted and held fordipping into the vats, and arrange for the mechanical low ering of thefiles into the respective vats. I also prefer to provide for circulationof the etching and washing fluids.

The final washing is preferably efi'ected in an alkaline water, say limewater.

I claim:

1. A process of renovating files and the like consisting in etching thecleaned Worn files by immersion in a warm bath of substantially equalparts of nitric acid, hydrochloric acid and water, at a temperature ofabout 100 F.

2. A process of renovating files and the like consisting in etching thecleaned Worn files by immersion in a bath composed essentially ofsubstantially equal parts of hydrochloric acid, nitric acid and Water,maintained at about 100 F., and thereafter washing, such washingoperation including washing with an alkaline solution.

In testimony whereof I have signed my name to this specification.

SAMUEL WHYTE.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. G.

